One form of an ignition system utilizes an ignition coil in which magnetic energy is stored. If the repetition frequency of the spark sequence is such that the stored magnetic energy is not completely dissipated at each breakdown of the spark gap, then only a shorter period of time is necessary for a subsequent pulse through the primary of the ignition coil in order to re-establish the required magnetic energy in the ignition coil itself. The first charge pulse, however, should be of sufficient length and intensity to completely store all the charge energy in the ignition coil which it is capable of holding.
It has previously been proposed, see, for example U.S. Pat. No. 3,926,557, to provide an ignition system in which repetitive spark pulses are generated by using a frequency generator which, repetitively, closes a control switch to permit current to flow through the primary of the ignition coil. If the frequency of operation of the frequency generator is high, then the exact timing of triggering of the first spark or breakdown of the spark plug cannot be reliably determined; if it is too low, then the number of breakdowns of the spark gap may be undesirably low.